One method known in the art for producing organosilicon compounds comprises reacting a silicon hydride containing compound with an unsaturated compound in the presence of a catalyst. This reaction is commonly referred to as hydrosilylation. Typically the catalyst is platinum metal on a support, a platinum compound generally used in an inert solvent, or a platinum complex, however other catalysts comprising rhodium or nickel may be used. In U.S. Pat. No. 2,823,218 to Speier, et al. a method for the production of organosilicon compounds by reacting an Si--H with a compound containing aliphatic carbon atoms linked by multiple bonds in the presence of a chloroplatinic acid is taught. U.S. Pat. No. 3,220,972 to Lamoreaux teaches a similar process however the catalyst is a reaction product of chloroplatinic acid. In EP Patent Application No. 0337197 to Lewis the catalyst used is a rhodium colloid and the silicon containing reactant must have two to three hydrogen atoms bonded to the silicon.
One of the major problems known in the art with hydrosilylations is the de-activation of the catalyst prior to the completion of the reaction. One method for reactivation of the catalyst has been to expose the reaction mixture to oxygen. For example, U.S. Pat. No. 4,578,497 to Onopchenko, et al. teaches the use of an oxygenated platinum containing catalyst for hydrosilylation with alkylsilanes, R'R.sub.x SiH.sub.3-x. The oxygenated platinum catalyst is produced by contacting the catalyst with an oxygen-containing gas. In particular, the catalyst is contacted with the oxygen-containing gas by bubbling air into the catalyst mixed with the olefin and with or without an inert solvent under ambient temperatures prior to the reaction. Another technique taught by Onopchenko is to run the hydrosilylation until de-activation occurs, cool to room temperature and then bubble an oxygen-containing gas into the mixture. Following the exposure to oxygen the system is placed under an inert atmosphere and the reaction is again commenced.
The method taught by Onopchenko has several disadvantages. The introduction of oxygen must always be done at room temperature. Therefore the oxygen must be introduced before starting the reaction. However, if an insufficient amount of oxygen is added then the catalyst may still de-activate, in other words, there is no control over the reaction except to stop and start the reaction. The oxygen can also be introduced once the catalyst has de-activated and the reactants have been cooled to room temperature. This results in inefficient processing and the possibility of unsafe conditions upon re-activation. Further, Onopchenko requires that the reactants be placed under an inert atmosphere after the exposure of oxygen, once again leading to the possibility of insufficient oxygen being present to sustain the reaction. Finally, Onopchenko does not provide any means for controlling the reaction rate through the use of oxygen, as in his disclosure, the reaction goes or it does not go.
Dickers, et al., "Organosilicon Chemistry. Part 24 Homogeneous Rhodium-Catalysed Hydrosilylation of Alkenes and Alkynes: The Role of Oxygen or Hydroperoxides", J. Chem. Soc., Dalton Trans. (1980) (2) 308; disclose the use of oxygen to initiate the hydrosilylation of propene, hex-1-ene and hex-1-yne using [RhCl(PPh.sub.3).sub.3 ] as the catalyst. The oxygen is necessary when the reagents have been purified.
Finally, in Harrod, J. F. and Chalk, A. J. "Hydrosilation Catalyzed by Group VIII Complex", Org. Synth. Met. Carbonyls. (1977) (2) 673-704, at pages 682 and 683, there is disclosed the fact that oxygen is a co-catalyst in hydrosilylations and that this is known among people who run hydrosilylations on a large scale where deliberate aeration of the reaction may be required to sustain catalytic activity. Chalk and Harrod merely reiterate that oxygen has an impact on hydrosilylation and on page 683, they speculate as to how it does impact hydrosilylation, but they never do disclose the key to controlling hydrosilylation.
Thus it is an object of this invention to provide a process for controlling hydrosilylation in a reaction mixture by controlling the solution concentration of oxygen relative to any platinum in said reaction mixture.
It is further an object of this invention to provide a process for controlling isomerization in linear or branched alkenyl compounds having at least 4 carbon atoms by introducing oxygen into the reaction mixture during the hydrosilylation reaction.
It is further an object of this invention to provide a means for producing dicycloalkylsubstituted silanes by reacting a silane selected from the group consisting of halo- or alkoxy- silanes having two hydrogen atoms bonded to the silicon or monocycloalkylsubstituted halo- or alkoxy- silanes having one hydrogen atom bonded to the silicon with an unsaturated cycloalkenyl compound or mixture of cycloalkenyl compounds having at least 4 carbon atoms in the presence of a hydrosilylation catalyst and oxygen.